前端传file 文件，后端实现断点上传oss的代码

前端传file文件可以使用HTML5的FormData对象实现，其中包含一个File类型的字段。后端实现断点上传oss的代码可以参考以下示例代码：

import oss2
import os
from flask import Flask, request

app = Flask(__name__)

# 初始化OSS客户端
auth = oss2.Auth('<AccessKeyId>', '<AccessKeySecret>')
bucket = oss2.Bucket(auth, '<Endpoint>', '<BucketName>')

@app.route('/upload', methods=['POST'])
def upload():
    file = request.files.get('file')
    chunk_size = 1024 * 1024  # 每个分片的大小，这里设置为1MB
    object_name = file.filename  # 对象名称，这里使用文件名作为对象名

    # 判断是否有上传记录，如果有则继续上传，如果没有则从头开始上传
    if 'upload_id' in request.args and 'part_number' in request.args:
        upload_id = request.args.get('upload_id')
        part_number = int(request.args.get('part_number'))
        part = request.data
        bucket.upload_part(object_name, upload_id, part_number, part)
        return 'Part uploaded successfully'

    # 初始化分片上传
    upload_id = bucket.init_multipart_upload(object_name).upload_id

    # 上传所有分片
    parts = []
    part_number = 1
    while True:
        part = file.read(chunk_size)
        if not part:
            break
        bucket.upload_part(object_name, upload_id, part_number, part)
        parts.append(oss2.models.PartInfo(part_number, oss2.utils.calc_md5(part, len(part))))
        part_number += 1

    # 完成分片上传
    bucket.complete_multipart_upload(object_name, upload_id, parts)
    return 'File uploaded successfully'

if __name__ == '__main__':
    app.run()

上述代码使用Flask框架实现了一个上传接口，前端可以通过POST请求将文件上传到该接口。后端将文件分成多个分片，然后逐个上传到OSS，并记录上传记录。如果上传过程中出现中断，可以利用上传记录继续上传未上传完成的分片。最后完成所有分片上传后，调用`complete_multipart_upload`方法完成分片上传。